Patent GB-213571-A (GB)
IPC: C01B21/26
Filed: 1924-03-24
Abstract: Ammonia is oxidized with air or oxygen in the presence of a heated mixture consisting of lead oxide with an oxide or oxides manganese, vanadium, molybdenum chromium, tungsten or uranium, in association with one or more alkaline earths.  Substances which yield the components of this mixture by oxidation may also be employed, e.g. hydrates, carbonates, peroxides, nitrates, nitrides, hydrides, or organic compounds of lead, manganese, barium, calcium, or strontium. During the oxidation, interaction takes place between the components of the mixture with the formation of plumbates, manganates, and manganites, and these substances may replace the original components. Preferably the mixture contains one atom of lead, one of manganese, and two of alkaline earth metal.  Reference is made to mixtures of calcium, strontium, or barium orthoplumbate with an oxide or oxides of manganese, and of calcium, strontium, or barium metaplumbate with calcium, strontium, or barium manganate or manganite.  The oxidation of the ammonia may be effected either intermittently or continuously. In the intermittent method, the process is carried out at a temperature of 250-500 DEG  C., whereby the nitrogen oxides produced are absorbed by the alkaline earths to form nitrates. Fresh alkaline earths or their hydrates may be added continuously or periodically. The ammonia oxidation is interrupted at intervals and the nitrates washed away with water.  The residue is dried, fresh alkaline earth added, and the mixture again employed in the ammonia oxidation. Before the washing, alkali carbonate may be added, whereby alkali nitrate is removed by the water and alkaline earth carbonate remains. Instead of washing away the nitrate, it may be decomposed by raising the temperature further. For the continuous operation, temperatures of 500-750 DEG  C. are employed, so that the alkaline earth nitrates formed are continuously decomposed.  The Specification as open to inspection under Sect. 91 (3) (a) describes also the absorption of the nitric acid vapours produced by dry agents, such as potassium or sodium carbonate, caustic lime, or soda lime, the remaining gases being submitted to wet absorption in the presence of air.  The following catalytic mixtures are also referred to, viz., barium orthoplumbate with molybdenum trioxide, vanadium pentoxide, tungstic acid, uranium trioxide, or chromic acid, and lead oxide with barium carbonate or nitrate and manganese dioxide.  Examples of the production and use of catalytic mixtures of particular composition are given. This subject-matter does not appear in the Specification as accepted.ALSO:Ammonia is oxidised with air or oxygen in the presence of a heated mixture consisting of lead oxide with an oxide or oxides of manganese, vanadium, molybdenum, chromium, tungsten or uranium, in association with one or more alkaline earths.  When the process is carried out at a temperature of 250-500 DEG  C., the nitrogen oxides produced are absorbed by the alkaline earths to form nitrates.  Fresh alkaline earths or their hydrates may be added continuously or periodically.  The ammonia oxidation is interrupted at intervals and the nitrates washed away with water. The residue is dried, fresh alkaline earth added, and the mixture again employed in the ammonia oxidation.  Before the washing, alkali carbonate may be added, whereby alkali nitrate is removed by the water and alkaline earth carbonate remains.  For the production of the catalytic mixture, substances which yield the components on oxidation may be employed, e.g. hydrates, carbonates, peroxides, nitrates, nitrides, hydrides or organic compounds of lead, manganese, barium, calcium or strontium. During the oxidation process, interaction takes place between the components of the mixture with the formation of plumbates, manganates and manganites, and these substances may therefore replace the original components.  Preferably the mixture contains one atom of lead, one of manganese and two of alkaline earth metal.  The Specification as open to inspection under Sect. 91 (3) (a) describes also the absorption of the nitric acid vapours produced by dry agents, such as potassium or sodium carbonate, caustic lime or soda lime, the remaining gases being submitted to wet absorption in the presence of air.  This subject-matter does not appear in the Specification as accepted.